This disclosure relates to an image reading apparatus.
Multifunction peripherals (MFP) becoming prevalent in recent years can read an image of an original document by scanning the original document with its scanner to generate image data of the original image, and then can output the original image onto a sheet of paper based on the image data, send the image data in a data file to personal computers, and send the image data via fax.
Especially, multifunction peripherals equipped with an auto document feeder (ADF) can deal with a plurality of sheets of an original document at one time. However, the original document may include blank sheets that a user does not want to copy or transmit, and therefore, in a case where a large number of original document sheets are processed through the ADF, the user takes a lot of time and effort to check for the absence of the blank sheets.
There have been proposed various techniques to detect such blank pages in original documents.
An image forming apparatus reads original documents to obtain the image data with pixel information, counts only pixels within a predetermined density range in the obtained image data, and compares the number of the pixels with a threshold value to detect blank pages in the original documents.
Another image processing apparatus detects blank pages in original documents by acquiring color occurrence frequency information about colors of all the pixels in the image data (histogram).
Furthermore, there are existing techniques for detecting blank pages in original documents that are made of colored paper or recycled paper with a low whiteness level shown as follows: (1) the first technique including determining whether original documents are made of colored paper or white paper, and in the case of colored paper, detecting blank pages by setting a threshold value, which is used to determine the presence or absence of pixels having a density, higher than the threshold value in the case of white paper; (2) the second technique including detecting blank pages based on variations in the number of black pixels within continuous lines; and (3) the third technique including detecting blank pages based on the number of pixels having a density per unit area between a margin area and a printed area.